Catalytic cracking



CATALYTIC CRACKING Filed Aug. 1a, 1959 4 Sheets-Sheet 1 y INVENTOR 0 Z2Ver E (ample/Z 129 O 9 p ww l0 ATTORNEYS Jum 1941 QF. EAMPBELL 24,345

- CATALYTIC CRACKING Filed Aug. 15, 1939 4 Sheets-Sheet 2 IZO i XNVENTOR ATTORNEYS June 17, 1941.

O. F. CAMPBELL CATALYTIC CRACKING Filed Aug. 16, 1939 4 Sheets-Sheet 4 M TU ATTORNEYS latter decreases.

Patented June l7 1941 cum I. Campbell, Whitin ma, assignor 0 Sinclair Refining Company, New York, N. Y., a

corporation of Maine Application August 16, 1939, Serial No. 290,399

10 Claims.

This invention relates to catalytic cracking ofhydrocarbons and provides improvements in ap paratus for cracking higher-boiling hydrocarbons to produce more valuable lower-boiling hydrocarbons in the presence of a catalyst.

In heretofore customary operations, the catalytic treatment of the hydrocarbons has been conducted in an intermittent manner. The hydrocarbons to be cracked, for example a petroleum stock, are vaporized by heating under a low pressure, usually in the presence of steam to resulting vaporous mixture of hydrocarbons, and

any steam, may range from 700-&00 F. to about 1000-1100 F.; the pressure may range from'subatmospheric to as high as 100 pounds per square inch or more. Depending upon the nature of the stock to be cracked, the temperature and pres: sure, and the proportion of steam employed, all or only a portion of the stock may be vaporized. When unvaporizedhydrocarbons remain these are usually separatedand removed prior to cata-- lyst contact. In any event, the vaporized hydrocarbons are sent to the cracking operation. There, in a reaction zone, a stream of the hydrocarbon vapors is passed in contact with a solid and usually porous or granular catalytic mass, such, for example, as fuller's earth or kieselguhr alone or admixed with various metals or metal salts. Lower-boiling hydrocarbons and carbon result from the ensuing cracking. The lowerboiling hydrocarbons and some of the carbon are onds, and, in certain catalytic cracking operations, the entire cycle time for cracking and regeneration may be less than a minute. This has necessitated the development of elaborate control mechanisms for automatically bringing about diversion of the stream of stock from a fouled catalytic mass to a regenerated one. Such conpromote vaporization. Thetemperature of the trol mechanisms not only increase plant investment and maintenance costs but are subject to operating diiiiculties. The regular production of a superior cracked product requires uniform opcrating conditions.

The heat of cracking reaction is composed of the heat of decomposition and theheat of recombinatiom Decomposition is endothermic and recombination is exothermic, and whether or not the reaction as a whole is heat-releasing or heatconsuming depends upon whether the heat of recombination or the heat of decomposition is greater. With most stocks to be cracked, at temperatures below about 975 F. the 'heat of decomposition generally is greater, so that below this temperature cracking generally is endothermic. Above 975 F. the heat of recombination usually is the greater so that above this temperature the reaction (considered as a whole) is exothermic. When the cracking in the region of catalyst contact is an endothermic reaction (as is more often the case) it consumes considerable removed from the reaction zone as formed, but

a substantial portion of the carbon adheres to the catalyst and coats its surfaces and chokes its pores as it accumulates. As the carbon accumulates and fouls the catalyst, the activity of the of hydrocarbon vapors to be cracked is diverted to another reaction zone containing a reactivated or regenerated catalyst mass, and the fouled mass is subjected to regeneration. This is usuallyac- When the economic limit of catalyst activity has been reached, the stream heat which may be supplied from the stock itself,

or from an exterior source as by conductiononly at the expense of additional and cumbersome equipment and in an inadequate manner.

As a result of my investigations, I have developed improvements in app ratus for the catalytic cracking of hydrocarbons which permits continuous cracking of a stream of hydrocarbon stock without diverting this stream periodically as the catalyst requires regeneration which permits a substantial gain in thermal eiiiciency through improved heat exchange between the cracking and regeneration phases of the cycle, and which aifords several advantages with re spect to control." Consequent upon these improvements, the cumbersome automatic controls heretofore necessary may be eliminated with resultant savings in costs for plant, operation, and

maintenance and with greater ease of operation and improvement in'products. These results are achieved in a process involving the contact of a catalytic mass with vaporized hydrocarbons with resultant cracking of the hydrocarbons and deposition of carbon on the mass and the subsequent treatment of the mass to remove the carbon therefrom prior to further contact of the mass with the hydrocarbons to be cracked by rotating the mass relatively'to certain zones'so that individual segments of the catalyst mass pass suc-. cessively and cyclically through a first zone to which the vaporized hydrocarbons to be cracked are supplied substantially continuously and from which the resulting cracked hydrocarbons are withdrawn substantially continuously, a second zone through which a purging fluid (such, for example, as superheated steam) is passed substantially continuously, a third zone through which a hot oxidizing gas is passed substantially continuously and in which the carbon deposited on the mass is burned and a fourth zone through which a purging fluid is passed substantially continuously to remove products of the carbon combustion from the mass prior to the reintroduction thereof into the first zone, while substantially uniform conditions are continuously maintained in all four zones, particularly the first.

The above described method is described and claimed in my copending application Serial No. 290,398, filed August 16, 1939, but is carried on advantageously in the apparatus of my invention which is described and claimed hereinafter.

This apparatus provides a casing divided into at least a cracking section and a regenerative section by radially extending baflles. These sections are sealed from each other, but enclose a concentrically mounted wheel divided into a plurality of segments in each of which is disposed a catalyst. The wheel is rotatable with respect to the various sections which enclose it, so that its catalyst segments may be passed continuously through the series of sections and thus be alternately employed to crack hydrocarbons passin continuously through the cracking section and be regenerated by hot oxidizing gases in the regenerative section. More specifically, the invention provides, in apparatus for the catalytic cracking of hydrocarbons, the combination which comprises a hollow head divided around its P riphery into a plurality of segmental chambers, said head having a flat bearing plate with ports therein communicating, respectively, with each of said chambers, a second hollow head disposed concentrically to the first head and having segmental chambers matching those in the first head with a fiat bearing plate having ports therein corresponding to those in the first head, said bearing plates being disposed concentrically and parallel facing each other and spaced apart a fixed distance, a catalyst carrier in the form of a wheel disposed between the two bearing plates with its axis coinciding with that of the two heads and rotatable relative to the heads, said carrier being divided into aplurality of segments or compar-tment-s by radial vanes extending substantially from one bearing plate to the other, a catalytic mass disposed in the compartments of the catalyst carrier, means for forcing vaporized hydrocarbons from a chamber of one head to a corresponding chamber of the other head in contact with the catalytic mass in a compartment, means i for sfinultaneously forcing a hot oxidizing gas from a second chamber of one head to a corresponding second chamber of the other head in contact with the catalytic mass in another compartment, and means for simultaneously rotating the wheel relative to the heads.

In the preferred form of the apparatus of my invention, the heads are annular, the catalyst carrier wheel is rigidly mounted on a shaft disposed on the common axis of the two heads and passing therethrough; means are provided for rotating the shaft; means are provided for preventing leakage of-vaporbetween the various sections of the apparatus; and the catalyst carrier is surrounded by an annular jacket for a hot diluent gas such as steam. The jacket space is enclosed by a drum fastened to the two heads so as to enclose.the carrier, and means are provided for supplying the diluent gas (say steam) to the jacket at a pressure in excess of that prevailing in any of the chambers so that leakage of gas. if any, will take place into the carrier compartments rather than out, thereby preventing leakage to the outside and undesirable admixture of hydrocarbons and oxidizing gases within the apparatus.

There may be two or more chambers in each of the heads but preferably there are at least four, comprising respectively (along the direction of rotation of the apparatus) a chamber for hydrocarbons, a second for a purging gas such as steam, a third for the oxidizing gas, and a fourth for a purging gas to remove the products of oxidation.

The number of compartments or segments in the catalyst carrier may be two or more, but preferably a large number (such as eighteen or twenty) is provided. In any case, the segments should be of such dimensions relative to the radial distance between the ports in the bearing plates that no one catalyst segment is in contact with the ports of different chambers in the same head at the same time; that is to say a segment should be out of contact with the port supplying hydrocarbon before it comes in contact with the port which supplies purging gas, etc. This may be assured by making the radial space between ports (i. e. the distance between them in the path of rotation) greater than the radial space or angle devoted to a single segment.

These and other features of my invention will be more thoroughly understood in the light of the following detailed description taken in conjunction with the accompanying drawings in which Fig. 1 is a plan view of apparatus of my invention having means for rotating a catalyst successivelylthrough a cracking zone, a purging zone, a regenerative zone, and a second purging zone;

Fig. 2 is a vertical section taken through the apparatus of Fig. 1 along the section line 2-2;

Fig. 3 is a horizontal section taken through the apparatus of Figs. 1 and 2 along the section line 3-3 of Fig. 2;-

Fig. 4 is another horizontal section taken through said apparatus along the line 4-4 in Fig. 2;

Fig. 5 is a developed vertical diagrammatic view of one form of the apparatus of my invention;

Fig. 6 is a section of a portion of the apparatus taken along the line 6-6 of Fig, 2 and showing a type of wiper seal for sealing the various zones of the apparatus from each other;

Fig. 7 is a diagrammatic flow sheet showing the disposition of the rotating catalyst apparatus of Figs. 1 .to 6 in a system for the catalytic cracking of hydrocarbons.

Referring now to the drawings and particularly {Ihis pipe is stationary.

to Figs. 1, 2' and a, it will be observed that in general the apparatus comprisesa vertical shaft assembly l upon which is rigidly mounted a annular heads It, l5. The inner wall of each head is formed by fiat annular parallel bearing plates I6, II. The heads are mirror images of each other and each is divided into four sections by radially extending bafiies. These sections correspond to a cracking zone l8,a first purging zone IS, a regenerative zone 20 and a second purging zone 2| (Fig. 3). The carrier wheel is adapted to rotate successively through these zones, carrying catalyst segments mounted thereon in contact with the hydrocarbons to be cracked, thence into contact with superheated steam or other purging gas in the first purging zone, thence into contact with an oxidizing gas in the regenerative zone and again into contact with the purging gas in the second purging zone.

To consider the apparatus ingreater detail,

1 substantially cylindrical catalyst carrier wheel at the upper and lower outer edges of the catalyst carrier wheel.

The space between the sheath and theouter shell of the carrier wheel is divided into a plurality of segmental compartments 35A, 85B, C, et seq. to SR by vertical radial baflles or vanes 56A to HR. inclusive, (Fig.- 4). Any desired number of compartments may be provided, but it is desirable to have a relatively large number of them, and, in the instant case eighteen compartments are provided. The vertical baflie plates extend substantially completely from top to bottom of the carrier wheel and have straight horizontal upper andlower edges 51, 53 close to and parallel with the inner surfaces of the bearing plates of the two heads. In the lower portion of each compartment a horizontal foraminous plate 58 or other catalyst supportis fastened. A

any of the conventional solid catalysts suitable the vertical shaft assembly is connected at its upper end through a variable speed reducer 22,

or other means for varying the speed of rotation, to a motor (not shown) The shaft assembly is hollow to permit water cooling. It is supported adjacent its lower end 23 by a thrust bearing 24 through which is passes. The shaft assembly at its mid-portion within the carrier wheel is enlarged and enclosed by a cylindrical wall 25 to form a cooling water chamber 26. A water inlet pipe 21 projects upwardly from-the base of the shaft to a point adjacent its closed upper end 23. Water forced into it througha lower water inlet 23 enters the cooling water chamber and flows downwardly'through the lower hollow portion of the shaft into a water outlet gland 3| disposed below'the thrust bearing and concentrically around the water inlet pipe. rotatably mounted on this gland, thus forming a sealed system. Water forced through the inlet pipe cools the interior of the shaft, flows downwardly through a rotatable coupling 32 disposed below the thrust bearing and out through the gland.

The carrier wheel H is rigidly fastened to the shaft adjacent its enlarged portion. Immediately adjacent the shaft, .the carrier wheel has an annular chamber 33 enclosed by a cylindrical sheath 34 and upper and lower annular walls 35, 36. This chamber is filled with non-inflammable heat insulating material 31 such as Sil-O- Cel.

The outer vertical wall of the carrier wheel is a cylindrical shell 38 that is separated from the sheath by a considerable annular space. At the top and bottom of the shell 38 are fastened, respectively, outwardly projecting peripheral labyrinth seal members 33, 43. These members are disposed adjacent the plates l6, I! that form the walls of the upper and lower heads, respec- The lower portion of the shaft is" the peripheral seal members.

tively. Each seal member has a series of concentric circular grooves 4!, 42, 43 and 44, 45, 43 in the surfaces that face the plates and into these fits a series of corresponding rings 41, 43. 49 and 50, SI, 52 that are fastened to the plates of the two casing heads thereby forming a pair of peripheral labyrinths, I3, 54, respectively,

for catalyzing the cracking of hydrocarbons. A number of such materials are known, among them being kieselguhr or fullers earth. The catalyst bed substantially fills the segmental compartments to a point just below the upper edge of the vanes. The catalyst bed should be porous or otherwise provide passage for gase therethrough in a vertical direction".

It will be observed that around the catalyst carrier wheel between its outer shell and the drum portion l3 ofthe casing there is an annular chamber lil This annular chamber or jacket space is enclosed at its upper and lower ends by However, unless these seals are perfect there is a tendency for gas under pressure to leak through the jacket space from one head to the other and thus by-pass the catalyst bed. With a view toward preventing such by-passing and also maintaining a proper temperature within the apparatus, steam is adtom of the carrier disk adjacent the space filledwith insulating material. In this instance, a

series of concentrically disposed rings 65A, 63, 66, and 88, 39, 13 are fastened, respectively, to. the upper and lower surfaces of the carrier wheel on the plates 35, 33 and project into peripheral concentric grooves HA, 1|, l2, and l4, I5, 16 formed in a, pair of upper and lower bearings l1, 18 through which the shaft passes. The labyrinth seals 63, 64 or other sealing device of like form, are necessary to prevent leakage of gases from the space above and below the catalyst bed outwardly to the atmosphere. If desired, packing material may be placed in the seals.

To consider the construction of the upper and Thus, the upper head chamber 8| is divided into a hydrocarbon chamber 83, a first steam chamber 84, an oxidizing gaschamber85, and"a second steam chamber 86 by radial baffles 81, 88, 88, 88, and these chambers are disposed, respectively, in the cracking zone I8, the first purging zone I8, the regenerative zone 28, and the second purging zone 2 I. Likewise, the lower head chamber 82 is divided into four corresponding segmental chambers 8I, 82, 83, 84 by baffles 85, 86, 81, 88 (see Fig. and these chambers are disposed, respectively, in the cracking zone, the first purging zone, the regenerator zone and the second purging zone.

The rotation of the carrier wheel is clockwise as viewed from above. Thus, as the wheel is rotated, any segment of the catalyst bed passes successively between the chambers 83, 8|, or hydrocarbon chambers of the upper and lower heads,

between the chambers 84, 82 or first steam chambers, between the chambers 85, 83 or oxidizing gas chambers, and between the chambers 86, 84 or second steam chambers.

As illustrated in Figs. 3 and 5, the hydrocarbon chambers occupy more than of the respective heads. Hydrocarbon vapors to be cracked enter the upper hydrocarbon chamber 83 through a feed pipe 88 of relatively large diameter, pass from this chamber through a port I88 that corresponds in radial space to five or six catalyst segments.

through these catalyst segments and a matching 7 outlet port |8| into the lower hydrocarbon chamber 8|. The resulting lower-boiling hydrocarbons are removed from this chamber 8| through an outlet pipe I82 of relatively large diameter.

Adjacent the hydrocarbon chambers, 84, 82 of the respective heads are the first steam chambers which occupy 3& 01"%3 of the respective heads. Steam is admitted into the upper chamber 84 through a pipe 84A, and passes into contact with the rotating catalyst carrier through a small port I83 in its bottom or bearing plate. This port 15 equal radially to about one catalyst segment and is disposed in the approximate center of the plate. The steam port I83 is separated from the hydrocarbon port I88 by a radial distance greater than that of one catalyst segment, so that such a segment must pass out of contact with the hydrocarbons before steam is admitted thereto. There is a corresponding steam port I84 in the plate of the matching lower steam chamber 82. Steam is admitted into the upper chamber 84 through a pipe 84A, and withdrawn from the lower chamber 82 through a pipe I86.

passes downwardly through the rotating catalyst segments into the corresponding lower chamber 83 of the lower head and is withdrawn therefrom through an outlet pipe 8.

The balance of the apparatus is occupied by the second purging section. This second purging section, like the first, corresponds radially to two or three of the catalyst segments. It contains the second steam chambers 86, 84 in the upper .and lower heads, respectively. Steam for purging is admitted into the upper chamber through an inlet pipe II I and passes through the adjacent catalyst segment to the steam chamber 84 in the lower head from whence the steam is withdrawn through an outlet pipe I I2. Both upper and lower chambers of the second purging section are provided with small pie-shaped ports H3, 4 (equal to about one catalyst segment) through whichthe steam passes into and out of the catalyst segments.

To prevent leakage between the various sections of the apparatus, the upper and lower edges of each of the vanes on the catalyst carrier wheel are provided with wiper seals which bear against the inner plates of the upper and lower heads. Such a seal is shown in detail in Fig. 6, and comprises a flexible brush I I5 fastened to the vane and bearing against the inside plate of the head. Seals of different construction may, of course, be provided but that illustrated is simple and effective.

The upperhead is provided .with four thermocouples H6, H1, H8, H8 disposed, respectively, in wells I28, I2I, I22, I23 in each of the several chambers to enable proper temperature control of the system. Like thermocouples in similar wells are provided in the chambersof the lower head.

A better idea of the operation of the apparatus described hereinbefore may be obtained by reference to Fig. 5 which is a developed diagram of the apparatus. Referring now to this diagram, it will be observed that oil vapor to be cracked is admitted in the hydrocarbon chamber of the upper head. It passes from this chamber through the hydrocarbon port (corresponding to about six segments of the carrier), through these six seg- Next around the periphery of the apparatus is the regenerative section in which are disposed the oxidizing gas chambers 85, 83. These chambers occupy approximately 95 to of the respective upper and lower heads. They are provided with a ments and the corresponding lower hydrocarbon port into'the lower hydrocarbon chamber from which it is withdrawn.

At the same time, steam is passed through the first purging section, entering first the steam compartment of the upper head, passing then through a small port (equal to about one catalyst segment) and then through the catalyst segment and the lower port into the steam chamber in the lower head. The steam, plus such substances as have been purged from the catalyst (principally entrained hydrocarbon gas) is withdrawn from the chamber in the lower head either independently or together with the cracked oil vapor from 1 the cracking section.

ing gas and the products of carbon combustion are then withdrawn and sent to waste or to a heat recovery system.

, tively large amount of heat. I my invention, this heatis supplied bythe rotat- At the same time that certain of the catalyst segments are being subjected to contact with oil vapors, others to contact with steam in the first purging section and still others to contact with hot oxidizing gas in the regenerative section, the

balance or the catalyst segments are treated in' it is withdrawn either alone or with the exhaust gases of the regenerative section.

As shown in Fig: 5, a control valve I24 is provided on the inlet line 99 for regulating the passage of oil vapor through the cracking section and a pair of valves I23, I21 are provided in branch pipes for regulating the proportions of air and steam'or inert gas supplied to the rcgenerative section through the pipe I03. Likewise,

control valves I28, I39 are provided for regulating the supply of steam to. the purging sections. Valves I30, I3I and I32, I33 are also provided on the outlets from the-purging sections so that gases therefrom may be passed through bypass lines I34, I35 and mixed, if desired, with the products of the cracking and regenerative sections or else handled separately. Thus, the valves I33, I3I on the outlet of the first purging section permit exhaust gases therefrom to be mixed with the product of the cracking section or handled independently. Likewise, the valves I32, I33 on ,the outlet of the second purging section permit exhaust gases therethrough to be handled inde-'- pendently or passedinto and mixed with the exhaust gases of the regenerative section. Another 1 valve I33 is provided for controlling the outlet of the regenerative ,section and regulating the pressure therein.

As indicated; especially in Fig. 2, the entire outer casing of the apparatus may be covered with a heat insulating jacket I31.

heat to the cracking zone, but with certain stocks and under certain conditions it may be necessary to extract heat. In either case, the apparatus that prevailing in the cracking zone, so that they act to extract heat.

The heat supplied and extracted from the rotating catalytic segments in the various zones will, or course, depend upon the specific heat, 1. e.

the heat containing capacity or a given mass oft the catalyst per degree oi, temperature, as well as upon thermal gradients existing between the several zones and the catalyst segments passing therethrough. Consequently, the catalytic mass should havea relatively high specific heat and the mass itself should be large enough to assure ample heat carrying capacity.

Assuming that the catalyst segments'are such v as to carry an adequate amount 01 heat to or from the cracking zone, the regulation '01 the amount oi! heat socarried can be controlled in various ways. If gases of constant specific heat. temperature and volume are passing through the purging and regenerative sections, the amount of heat supplied to the cracking zone may be altered by varying the speed of rotation oi-the catalyst carrier. On the other hand, the amount or heat introducedinto the catalyst carrier and supplied to the cracking zone may .be varied by varying the temperature of the purging gases, or by varying the temperature of the oxidizing gases passed in contact with the catalyst in the regenerative zone. Since the great bulk of the-heat supplied to the catalyst is supplied in the regenerative zone, this is a satisfactory point at whichto regulate the amount or heat supplied. This regulation may be brought about by changing the temperature or the specific heat or both 01' the gases passed through the regenerative zone. However, this regulation of heat in the regenerative zone cannot be regulated without regard to the oxidizing characteristics or capacities oi the gases passing therethrough. Consequently, it is convenient to provide, as illustrated in Figure 5, a source of hot oxidizing gas and o! a hot diluent or inert ,gas; which may be inert carbonaceous gaseous been attained, and assuming thecorrect speed of rotation of the catalyst carrier, the exact amount,

of heat necessary for the promotion oI. the catalytic cracking reaction may be supplied. By

' this means constant conditions can be mainhereindescrlbed provides convenient means for regulating the heat supplied to the cracking zone or-removed therefrom, by varying the amount of heat contained in the rotating catalyst segments.

If, for example, the particular cracking reaction being carried out is strongly endothermic, it is necessary tosupplyto the cracking zone a-relathermic the rotating catalyst segments are cooled in the zones other than the cracking zone, and

are returned to the latter ata temperature below In accordance with tained in :all of the zones of the. apparatus and constantstreams at constant temperatures 0! both reaction products and reactivation products are available for further economical recovery or waste heat.

By varying the speed of rotation of the catar lyst wheel or carrier,'the cycle of processing and the desired speed of rotation for a given stock has been established, the character and amount of oxidizing gas employed in reactivation may be controlled so as toburn Irom the catalyst the desired proportion of the carbon content de-' posited thereon. Thus, if desired, all of the carbon may be burned out of the catalyst. How? ever, it is preferable to burn substantially only the surface carbon from the catalyst, leaving some deposit of carbon within the pores oi! the mass. Operations so conducted result in an increased yield of more valuable hydrocarbons with a minimum degradation or conversion of hydrocarbons to elemental carbon.

In the event that the heat of reaction cannot be supplied in the reactivation zone either from the heat of combustion, or from the sensible heat of gases introduced therein while maintaining an optimum catalyst efliciency, the-apparatus may be divided into five sections rather than four, the additional section being used for raising or lowering the temperature or the catalyst bed by means of team, inert gas, or by passing the gaseous product of reactivation through the mass. Moreover, by varying the temperature'and quantity oi preheated steam or other purging gas passed through the purging section, the amount of heat picked up by the rotating catalyst may be varied to some degree.

As indicated hereinbeiore, the sealing steam introduced into the jacket space between the catalyst wheel and the drum of the casing tends to leak into the oil vapor being cracked as well as into the inert gas or steam-air mixture passed through the regenerative section. For this reason, the'steam employed for sealing should be maintained at a temperature sufllciently high that leakage thereof into the apparatus will not reduce the temperature of the vapor streams, especially the stream of hydrocarbons. Hence, it is necessary to superheat the steam employed for sealing to a temperature slightly in excess of that 01' the oil vapors being treated in the cracking zone. Superheating the steam ofiers a further advantage by serving to reduce the amount of steam required for sealing.

In order to minimize steam consumption in the apparatus and especially steam consumption due to leakage, it is desirable to maintain the pressure of the gases employed in reactivation substantially the same as the pressureof the oil vapor entering the cracking zone while maintaining slightly higher pressures on the steam entering the purging zones and the sealing zone.

To minimize leakage from. zone to zone at the bottom of the carrier wheel a back pressure should be maintained on the products from the reactivation zone substantially equal to the back pressure on the oil vapors leaving the cracking zone while maintaining a back pressure at the bottom of the two-purging zones equal to or slightly in excess of the back pressures maintained at the bottom of the cracking zone and at the bottom of the reactivation zone.

In order to maintain the desired pressure in the reactivation zone while varying the supply be left between the radially spaced ports of both upper and lower heads to prevent any catalyst carrier segment of the carrier wheel from coming in contact with two zone at the same time. 'I'hus,- any individual segment of the catalyst carrier must pass completely'out from under a port into the cracking zone before it passes under the port in the first purging zone, et seq.

The apparatus of Figs. 1 to 6 may be incorporated into a variety or hydrocarbon cracking systems, and utilized in conjunction with a variety of equipment for recovering and separating the cracked hydrocarbons. One means of utilizing the apparatus is illustrated in Fig. '7 which is a flow sheet of a catalytic cracking system including the rotating catalyst apparatus hereinbefore described. In this system, a petroleum stock I50 to be cracked is mixed with an appropriate amount of steam I5I and the mixture is passed to a heater I52 which vaporizes the oil substantially completely. From the heater a mixture I53 of oil vapor and steam (say, in equimolecular proportions) passes to a cracking apparatus I 54, constructed as described in detail hereinbefore and indicated diagrammatically on Fig. 7. The oil vapor and steam mixture passes through the cracking section of the apparatus as the catalyst carrier thereof is rotated (at a speed of say, two revolution per minute) and the oil 'is cracked and withdrawn in a mixture I55 of steam and vapors of lower boiling hydrocarbons at the lower portion of the apparatus.

A supply of steam I56 for operating the purg ing sections of the cracking apparatus, for admixture with hot air for the regenerative section and for sealing purposes is passed through a superheater I51, and there heated to a temperature in excess of that of the oil entering the cracking section. Part of this superheated steam is passed through a line I58 into the space between the catalyst wheel and the drum of thecasing, from which it may leak through the labyrinthian seals into any 01 the sections or the apparatus but in so doing prevents leakage outwardly from these sections. Another part of the superheated steam passes through a line I59 into the first purging section of the apparatus and sweeps out 01. the catalyst segments that rotate therethrough residual oil vapors. The steam from the first purging section is permitted to intermingle with the cracked hydrocarbons exhausted from the cracking apparatus to form the mixture I55 and through a. pipe line III the so as to maintain a sub'stantiallyconstant volume flowing through the catalyst. This will permit the maintenance or a pressure drop through the reactivation zone equivalent to the pressure drop of the oil vapors passing through the cracking zone. The valves provided in the apparatus, as illustrated in Fig. 5, permit such variations.

Generally speaking, the portion of the apparatus employed as a regenerative zone should be approximately the same in size as that employed in cracking and both should occupy several times as much space as the purging sections. However, when it is necessary to supply a very large amount" 01 heat to the cracking zone, it may be desirable to reduce the size of the cracking zone as compared to the regenerative zone thereby increasing the heat transfer therebetween. It

thence into the line Ill.

mixture is sent to a flash tower I 60A.

A third portion or the steam from the superheater may be mixed with hot compressed air and inert gases in a pipe line-Iii and passed through the regenerator section or the cracking apparatus. To produce the hot compressed air, atmospheric air is first compressed in a compressor I62, passed through a heater I83 and The inert gases for diluting the air and thus impeding the combustion of the carbon on the catalyst segments passing through the regenerative section may be produced by burning carbonaceous fuel I in hot compressed air delivered to an inert gas generator I65 through a pipe line I 65. From the inert gas generator the inert gas, in which the oxygen has been substantially all consumed is sent into the pipe line ISI.

superheated steam is admitted to the second purging section through a conduit I61, and after passing through therotating catalyst segments condition.

is withdrawn from the lower head and may be passed to waste either independently or mixed with the exhaust-gases from the regenerative section through a stack I88.

When the petroleum stock to be cracked is a relatively light oil which can be completely vaporized under prevailing temperature and pressure conditions, say a temperature ranging from 800 to 1000 F. and a pressure ranging from subatmospheric to in excess of 100 pounds per square inch, it is not necessary to remove unvaporized hydrocarbons prior to introduction of the mixture of oil and steam into the cracking apparatus. Otherwise,- a flash. chamber (not shown) should be disposed between the heater and the without release or pressure.

compressed overhead is then mixed with part of the bottomswithdrawn from the receiver.

The mixture of receiver bottoms and compressed overhead is passed through a line I88 to a high pressure receiver I81 and subjected to a further operation from which gas and liquid are separated under a pressure of approximately 250 pounds per square inch. Such separation gives a gaseous end product that is relatively free from hydrocarbons that should be included in the liquid product or distillate.

The distillate 188 from the high pressure receiver, i. e. the bottoms product orliquid resulting from the separation under high pressure,.is sent to a conventional stabilizer I89 from which a distillate I98 of the desired vapor pressure is drawn on? as "a bottoms product. Overhead gas or by introduction of i'ractionating column bottoms to give a desired tar gravity preferably less than 10 A. P. 1. Both types'of control are provided for in the apparatus illustrated in Fig. 7. Thus, tar may be withdrawn from the bottom of the flash tower through a line I 68 and part of the tar forced through a pump I10 back into the i'lwh tower with or without cooling in a cooler The flash tower overhead I12 passesto ,a trace tiona'ting tower I13. Here two gas oil cuts may I8I from the stabilizer normally is diverted together with the overhead I82 from the high pressure receiver to a polymerization plant for conversion of these gases to higher olefine for polymer gasoline.

I claim:

1. In apparatus for the catalytic cracking of hydrocarbons, the combination which comprises a hollow annular head divided around its periphery into a plurality of segmental chambers,

said head having a flat bearing plate with ports therein communicating respectively with each of said chambers, a second hollow annular head disposed concentrically with the first head and having segmental chambers matching those in the first head with a flat bearing plate having ports thereincorresponding to those in the bearing plate of the first head, said bearing plates being disposed concentrically and parallel facing be taken oflE-one as a side'stream I14 and one as a bottom cut I15. Either or both' of these streams may be recycled throughthe system for further processingand may be returned-to the towersystem either hot or cold, as desired. In the apparatus illustrated in Fig. 'Lprovision is made only for recirculating the bottom out through a pump I18 and optionally either through a cooling'coil I11 or directly in the hot In the apparatus illustrated in Fig. 'l-the side stream cut is passed through the cooler I18 and thence is withdrawn .from

the system for further. processing.

each other and spaced apart a fixed distance, a catalyst carrier wheel disposed'between the two bearing plates with its axis coinciding with that of .the two heads and rotatable relative to the heads, said'carrier wheel being divided into a plurality of compartments by radial vanes ex- I tending substantially from one bearing plate. to the other, a catalytic mass disposed in the compartments of the catalyst'wheel, means for forc-' ins; vaporized hydrocarbons from a chamber of one head to a corresponding chamber of the other headin contact with thecatalytic mass in one compartment, means for simultaneously forcing a ,hot oxidizing gas from a second chamber '0! one head to a corresponding secondv chamber of thefother head in contact with the catalytic mass The overhead stream I18 or the fractionating tower is controlled to give a product within finished gasoline distillation range specifications.

The overhead from the fr'actionating' column is withdrawn and passed through a cooler I88 into a receiver I8I. A portion of the condensed fractionator overhead (receiver bottoms) IIIA may be returned from this receiver as reflux 'to the top of the fractionating column through a pump I82 and a line I 83 for controlling the tempera-. ture of the top or this column.

The apparatus otFig. 7 is designed for low pressure operation, in which case agaseous overhead product I oi the receiver I8I (i. a., the portion of the fractionating column overhead which remains uncondensed) is withdrawn from this receiver and wouldcontain a large portion of hydrocarbons which should be retained in the final stabilized distillate. With this in mind, the overhead I88 from the receiver is passed through in another compartment, and means for simultaneously rotating the carrier wheel relative to the heads.

2. In apparatus for the catalytic cracking of hydrocarbons, the combination which comprises a hollow head divided around its periphery into "a plurality of segmental chambers, said head having a fiat'bearing plate with ports therein communicating respectively with each oi said chambers, a second hollow head disposed concentrlcally with the first head and having se mental chambers matching those in the first head with a fiat bearing plate having ports therein corresponding to those in the bearing plate of the first head, said bearing plates being a compressor I88 and compressed to a pressure slightly above that desired for stabilization. The

disposed concentrically and parallel facing each otherand spaced apart a fixed distance, a catalyst carrier wheel. disposed between the two bearing plateswithits axis coinciding with that of the twoheads and rotatable relative to. the heads,

said carrier wheel being'divided into a plurality of compartments by radial vanes extending substantially from one bearing plate to the other, a

catalytic mass disposed in the compartments of the catalyst wheel, means for forcing vaporized hydrocarbons from a chamber of one head to a corresponding chamber of the other head in contact with the catalytic mass in one compartment, means for simultaneously forcing a hot oxidizing as from a second chamber of one head to a corresponding second chamber of the other head in contact with the catalytic mass in another compartment, means for simultaneously rotating the carrier wheel relative to the heads, an annular jacket surrounding the carrier wheel and fastened to the two heads and means for introducing a hot diluent gas into said jacket.

3. In apparatus for the catalytic cracking of hydrocarbons, the combination which comprises a hollow head divided around its periphery into at least four segmental chambers, said head having a fiat bearing plate with ports therein communicating respectively with each of said chambers, a second hollow head disposed concentrically with the first head and having segmental chambers matching those in the first head with a fiat bearing plate having ports therein corresponding to those in the bearing plate of the first head, said bearing plates being disposed concentrically and parallel facing each other and spaced apart a fixed distance, a catalyst carrier wheel disposed between the two bearing plates with its axis coinciding with that of the two heads and rotatable relative to the heads, said carrier wheel being divided into a plurality of compartments by radial vanes extending substantially from one bearing plate to the other, a catalytic mass disposed in the compartments of the catalyst wheel, means for passing hot hydrocarbon gases from a chamber in one head to the corresponding chamber in the other head, means for passing a hot purging gas from the second chamber in one head to the corresponding second chamber in the other head, means for passing a hot oxidizing gas from the third chamber in one head in contact with the catalyst to the corresponding third chamber in the other head, and means for passing a hot purging gas from the fourth compartment of one head into the corre spending fourth compartment of the other head.

4. In apparatus for the catalytic cracking of hydrocarbons, the combination which comprises a hollow head divided around its periphery into a plurality of segmental chambers, said head having a fiat bearing plate with ports therein communicating respectively with each of said chambers, a second hollow head disposed concentrically with the first head and having segmental chambers matching those in the first head with a fiat bearing plate having ports therein corresponding to those in the bearing plate of the first head, said bearing platesbeing-disposed concentrically and parallel facing each other and spaced apart a fixed distance, a catalyst carrier wheel disposed between the two bearing plates with its axis coinciding with that of the two heads and rotatable relative to the heads, said carrier wheel being divided into a plurality of compartments by. radial vanes extending substantially from one bearing plate to the other, wiper type seals disposed between the bearing plates and the adjacent edge of the vanes, a catalytic mass disposed in the compartments of the catalyst wheel, means for forcing vaporized hydrocarbons from a chamber of one head to a corresponding chamber of the other head in contact with the catalytic mass in one compartment,

gas from a second chamber of one head to a corresponding second chamber of the other head in contact with the catalytic mass in another compartment, and means for simultaneously rotating the carrier wheel relative to the heads.

5. In apparatus for the catalytic cracking of hydrocarbons, the combination which comprises a hollow head divided around its periphery into a plurality of segmental chambers, said head having a fiat bearing plate with ports therein communicating respectively with each of said chambers, a second hollow head disposed concentrically with th first herd and having segmental chambers matching those in the first head with a fiat bearing plate having ports therein corresponding to those in the bearing plate of the first head, said bearing plates being disposed concentrically and parallel facing each other and spaced apart a fixed distance, a catalyst carrier wheel disposed between the two bearing plates with its axis coinciding with that of the two heads and rotatable relative to the heads, said carrier wheel being divided into a plurality of compartments by radial vanes extending substantially from one bearing plate to the other, a catalytic mass disposed in the compartments of the catalyst wheel, means for forcing vaporized hydrocarbons from a chamber of-one head to a corresponding chamber of the other 'head in contact with the catalytic mass in one compartment, means for simultaneously forcing a hot oxidizing gas from a second chamber of one head to a corresponding second chamber of the other head in contact with the catalytic mass in another compartment, means for simultaneously rotating the carrier wheel relative to the heads, a drum surrounding the catalyst carrier wheel and joined to the two heads, andperipheral seals adjacent the points at which the drum joins the respective heads to prevent gas by-passing from one head to the other without passing through the carrier I wheel.

6. In apparatus for the catalytic cracking of hydrocarbons, the combination which comprises a hollow annular head divided around its periphery into a plurality of segmental chambers, said head having a fiat annular bearing plate with ports therein communicating respectively with each of said chambers, a second hollow annular head disposed concentrically with the first head and having segmental chambers matching means for simultaneously forcing a hot oxidizing those in the first head with a flat annular hearing plate having ports therein corresponding to those in the first head, said bearing plates being disposed concentrically with, parallel to and facing each other, a rotatable shaft disposed on the common axis of the two heads; a rotatable catalyst carrier wheel rigidly mounted on the shaft between the two bearing plates, said carrier bein divided into a plurality of segments by radial vanes and extending substantially from one bearing plate to the other, a catalytic mass disposed in the segments of the carrier wheel, means for forcing vaporized hydrocarbons from the chamber of one head to the corresponding chamber of the other head in contact with a catalytic mass in .a segment, means for simultaneously forcing a hot oxidizing gas from a second chamber of one head to a corresponding second chamber of the other head in contact with the catalytic mass in another segment and means for simultaneously rotating the shaft.

7. In apparatus for the catalytic cracking of hydrocarbons, the combination which comprises a hollow annular head divided around its pethose in the first head with a flat annular bearing plate having ports therein corresponding, to those in the first .head, said bearing plates being disposed concentrically with, parallel to and facing each other, a hollow rotatable shaft disposed on the common axis of the twoheads, means for forcing a cooling fluid through the hollow shaft, a rotatable catalyst carrier wheel rigidly mounted on the shaft between the two bearing plates, said carrier being divided into a plurality of segments by radial vanes and extending substancatalytic mass disposed in the segments of the carrier wheel, means for forcing vaporized hydrocarbons from the chamber of ,one head to a corresponding chamberof the other head in contact with a catalytic mass in a segment, means for simultaneously forcing a hot oxidizing gas from a second chamber of one head to a corre- ,ripheryinto a plurality of segmental chambers,

said head having a flat annular bearing plate with ports therein communicating respectively with each of said chambers, a second hollow annular head disposed concentrically with the first head and having segmental chambers matching those in the first head with a flat annular bearing plate having ports therein-corresponding to head witha flat bearing plate having radially spaced ports therein corresponding to those in the bearing plate of v the first head, said bearing plates. being disposed concentrically and parallel facing each other and spaced apart a fixed distance, a catalyst carrier wheel disposed between the two bearing plates with its axis coincidingwith that of the two heads and rotatable relative to the heads, said carrier wheel being Holly from one bearing plate to the other, a

those in the first head, said bearing plates being disposed concentrically with, parallel to and facing each other, a rotatable shaft disposed on the common axis of the two heads, peripheral seals on the respective bearing plates adjacent the shaft, a rotatable catalyst carrier wheel; rigidly mounted on the shaft-between the two bearing plates, said carrier being divided into a plurality of segments by radial vanes and extending substantially from one bearing plate to the other, a catalytic mass disposed in the segments. of the carrier wheel, means for forcing vaporized hy-' drocarbons from the'chamber of one head to a corresponding chamber of the other head in contact with a catalytic mass in a segment, means for simultanenously forcing a hot oxidizing gas from a second chamber of one head to a corresponding second chamber of'- the other head in contact with'th'e'catalytic mass in another segment and means for simultaneously rotating the shaft.

divided intoa plurality of compartments by radial vanes extending substantially from one bearing plate to the other, a catalytic mass disposed in the compartments of the catalyst wheel. means for passing hothydrocarbon es from a chamber in one head to the co esponding chamber in the other head, means for passing a purging gas from the second chamber in one head to the corresponding second chamber in the other head, means for passing an oxidizing gas from the third chamber intone head in contact with the catalyst to the corresponding third chamber in the other head, and means for passing a purging gas from the fourth compartment of one head into the corresponding fourth compartment of the other head, the. distance between the radially spaced ports in the bearing plates along the direction of rotation of the wheel being greater than the width of the compartments of the carrier wheel in the same direction. l i

10 In apparatus for the catalytic cracking of hydrocarbons, the combination which comprises a hollow annular head divided around its periphery into a plurality of segmental chambers,

said head having a flat bearing plate with radially spaced ports therein communicating respectively with each oi said chambers, a second hollow annular head disposed concentrically with the first said bearing plates being disposed concentrically and parallel facing each other and spaced apart a fixed distance, a catalyst carrier wheel disposed between the two, bearing plates with its axis coinciding with that of the two heads and rotatable relative to the heads, said carrier wheel being divided into a plurality of compartments by radial vanes extending substantially from one bearing plate to the other said radial vanes being radially spaced apart a distance substantially less than the radial width of said ports, a catalytic, mass disposed in the compartments-of the catalyst wheel, means for forcing vaporized hydrocarbons from a chamber of one headto a corresponding chamber of the other head in con- 9. In apparatus for 'the catalytic cracking of hydrocarbons, the combination which comprises a hollow head divided around its periphery into at least four segmental chambers, said head having a flat bearing plate with radially spaced ports therein communicating respectively with each of said chambers, a second hollow head disposed tact with the catalytic mass-in one compartment, means for simultaneously forcing a hot oxidizing gas froma second chamber of one head to a corresponding second chamber of the other head in contact with the catalytic mass in another compartment, and means for simultaneously rotating the carrier wheel relative to the heads.

' OLIVER F. CAMPBELL.

- concentrically with the first head and having segmental chambers matching those in the first 

